The relationship between Stress-Energy tensor and Mass

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Discussion Overview

The discussion revolves around the relationship between the Stress-Energy tensor and mass in the context of Einstein's field equations. Participants explore how mass distributions relate to the Stress-Energy tensor, particularly focusing on its components and implications for space-time curvature.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant states that every mass distribution should have an associated Stress-Energy tensor and questions the nature of that relationship.
  • Another participant identifies the volumic mass density as the 00 component of the Stress-Energy tensor.
  • It is noted that energy density is proportional to mass density only for a body at rest.
  • Several participants inquire about the other components of the Stress-Energy tensor beyond the 00 component.
  • One participant mentions that for a fluid at rest, the spatial components of the Stress-Energy tensor correspond to pressure.
  • Another participant points out that the off-diagonal terms of the tensor represent shear stresses.
  • Momentum density is introduced as relevant when considering moving objects or fluids.

Areas of Agreement / Disagreement

Participants express curiosity about the components of the Stress-Energy tensor, indicating a lack of consensus on the full implications and interpretations of these components. Multiple viewpoints regarding the significance of different tensor components are present.

Contextual Notes

The discussion does not resolve the complexities surrounding the relationship between mass and the Stress-Energy tensor, nor does it clarify the implications of various tensor components in different scenarios.

ShayanJ
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In Einstein field equations,the term that is responsible for curving Space-Time is the Stress-Energy tensor.But we know that mass should be able to curve space-time.So I think every mass distribution should have a Stress-Energy tensor associated with it.
What is that relationship?
Thanks
 
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Volumic mass density is the 00 component of the stress-energy tensor.
 
Shyan said:
In Einstein field equations,the term that is responsible for curving Space-Time is the Stress-Energy tensor.But we know that mass should be able to curve space-time.So I think every mass distribution should have a Stress-Energy tensor associated with it.
What is that relationship?
Thanks

The relationship is explained in Wikipedia here: http://en.wikipedia.org/wiki/Stress–energy_tensor

The simplest case is a perfect fluid at rest. In that case, the nonzero components of the stress-energy tensor [itex]T^{\alpha \beta}[/itex] are:
[itex]T^{0 0} = \rho[/itex], where [itex]rho[/itex] is the mass-energy density, and
[itex]T^{1 1} = T^{2 2} = T^{3 3} = p[/itex], where [itex]p[/itex] is the pressure.
 
dextercioby said:
Volumic mass density is the 00 component of the stress-energy tensor.
Energy density, which is proportional to mass density only for a body at rest.
 
Thanks guys
But what about other components?
 
Shyan said:
Thanks guys
But what about other components?

As I said, for a fluid at rest, the three spatial components of the stress-energy tensor are just the pressure.
 
Shyan said:
But what about other components?

The diagram on the Wikipedia page identifies what the various components (or groups of them) represent.
 
Shyan said:
Thanks guys
But what about other components?

In addition to what Steven said, the off diagonal terms are shear stresses.
 
And of course you have momentum density...if you have a moving object or fluid.
 

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